Although there have been substantial numbers of studies conducted in the last ten years to document the incidence and prevalence of substance use (particularly alcohol and tobacco) among adolescents, and to understand the factors which account for substance use behavior among adolescents, there have been relatively few longitudinal studies undertaken to examine the relationships between family functioning and substance use behavior of adolescents. Rarely has data about substance use patterns along a continuum of use been obtained independently from all family members--parents, young adolescents and their older siblings been obtained. The purpose of the proposed study is to focus on the nonuse, initiation, continuation, transition (use to abuse) and cessation of use of tobacco, alcohol and other substances by young adolescents (12 and 13) in relationship to familial functioning (family adaptability and cohesion, family life events and coping), parental and older sibling substance nonuse/use and young adolescent locus of control and life events and coping, their substance nonuse/use, their perceptions of peer use and attitude toward these substances. Five hundred families chosen randomly from the membership of a large maintenance organization will have at least one adolescent 12-13 years old; the study will include all older adolescent siblings (ages 14-18) currently living at home. The sample focuses on normal families, i.e., selected by criteria other than substance use of adolescents. A Research Assistant/Interviewer will take the instruments to the families homes for administration. The instrument will be completed separately by each family member. Each of the variables of interest is measured through the use of carefully chosen, already established instrumentation. Several instruments were developed for the pilot study. Two follow-up surveys will be undertaken at one year and at two years after the respondent families have been initially surveyed. The data will be examined from both a cross-sectional prespective and as part of a longitudinal strategy. Several statistical procedures will be used to analyze the data. Multivariate analysis strategies will be employed, along with other data analytic strategies, to assess the relative importance of different factors as predictors of adolescent substance use.